Longitudinal comparison of the development of VLBW infants using the Bayley scale

Objective: In this study, developmental features of children with very low birth weight（VLBW）were examined longitudinally using the Bayley Scales of Infant and Toddler Development-Third Edition（Bayley-III）. Methods: All VLBW infants examined were born in Toyama University Hospital of NICU between August 2010 and December 2014. Sixty-six VLBW infants were assessed using the complete Bayley-III at 18 months corrected age and 36 months. In addition to the longitudinal score comparison, we set the reference point for development delay for five scaled scores to values less than −1 SD, classified the participants into three groups （non-catch-up group ［NCU group: delayed at both 18 months corrected age and 36 months］, catch-up group［CU group: delayed at 18 months corrected age but healthy at 36 months］, and good progress group［GP group: healthy at both 18 months corrected age and 36 months］）, and then compared groups. Results: In the longitudinal comparison, the language composite score significantly improved（p＝0.000）. The NCU group comprised 24 infants, the CU group comprised 21 infants, and the GP group comprised 21 infants. There was no significant difference in the clinical background in these 3 groups, but there was a difference in the longitudinal score change in the 3 groups. Comparing the scaled scores at 18 months corrected age between the three groups, the cognitive and gross motor scores were significantly lower for the NCU group（cognitive: p＝0.033, gross motor: p＝0.002）. Conclusions: These results suggest that VLBW children between 18 months corrected age and 36 months of language development were remarkable, but when classified according to the developmental process, the developmental status varied among these children. Therefore, we suggest that the low cognitive and gross motor score recorded at 18 months corrected age were features of the group with a high risk for developmental delay at 36 months.